2015年6月24日星期三

Best Practices in PCB Design: Exporting Gerber Files


Best Practices in PCB Design: Exporting Gerber Files



Overview

This document provides Ultiboard users with practical tips and recommendations on what to do when exporting a PCB design to fabrication.

This document will discuss how to best work with the Ultiboard design environment to generate Gerber files and NC drill files to send to a fabrication house such as Sunstone Circuits.

This is the second in a series of articles that:
  1. Help you finalize for fabrication in Ultiboard
  2. Discuss exporting Gerber files for prototype fabrication
  3. Provide a step-by-step check-list before prototype fabrication

Table of Contents

  1. Creating the Gerber files for PCB Manufacturer
  2. Drill Tables
  3. Next Step

1. Creating the Gerber files for PCB Manufacturer

After verifying all components and completing the final PCB checks, the Gerber files will need to be generated and  uploaded to the board manufacturer’s web page.
For more information on the Gerber Export dialog process, please view this article which provides more context to the dialog box, and what the various settings mean.
Exporting Gerber Files from NI Ultiboard

Gerber Properties

To begin generating the PCB files, the settings for each of the various file types will need to be established.  The first files needed are the Gerber files which allow the manufacturer to create the basic artwork for each of the layers.  From the menu:
  1. Launch the Export setup window from the menu by selecting File > Export….
  2. Ultiboard has default settings for different export schemes such as Fabrication or Fabrication and Assembly
  3. To export Gerbers and Drill files select Fabrication from the drop down menu and the units system used by your board manufacturer
Figure 1 - Export Dialog Box

The RS-274X standard is preferred as it is the most current and widely used Gerber format and automatically assigns the D-code aperture setting whereas the RS-274D requires the manual setup of aperture settings. Aperture D-codes set the basic drawing tool sizes and styles used by the manufacturer to physically create the various layers of the PCB.
In the Gerber properties window, the following Available Layers will be automatically selected, you can add more layers to the export if needed.
  1. Board Outline
  2. All copper layers (Copper Top, Copper Inner 1, Copper Inner 2, Copper Bottom, etc…)
  3. Drill (may be optional for quick turn PCB services using standard drill sizes)
  4. Drill Symbols (may be optional for quick turn PCB services using standard drill sizes)
  5. Silkscreen Top and Silkscreen Bottom (for single sided boards only the top silkscreen layer may be required)
  6. Solder Mask Bottom and Solder Mask Top (may be optional for quick turn PCB services)

It is important to complete the following steps to finalize export: 
  • In the Units section select Imperial (Mil)
  • In the Digits section, select integer 2 and decimal place 4
  • Oversize the Soldermask based on PCB manufacturer’s recommendations (some quick-turn PCB manufactures suggest over sizing the PCB mask to allow for adequate spacing around pads for the solder mask tolerances).
 Now, go the the Output Configuration tab and this where you can define where all the Gerber and Drill files will be saved on your computer. By default it will be set to the same directory where your design file is saved.
Figure 2 - Export Dialog Box Output Configuration



2. Drill Tables

In any PCB, there are typically many holes that need to be drilled for things such as through-hole parts, vias and mounting holes.   There are multiple files relating to the drilling of the holes in the PCB.  The one essential in the creation of the PCB is the NC Drill file (NC = Numerically Controlled).  The NC Drill export selection will create two files, a ‘.drl’ and ‘.rep’. 
The rep is a report file listing a summary of the drill sizes and quantities.  The drill sizes are associated with an individual drill bit (i.e. “tool”) so the tool numbers (“T#”) are shown as each individual sized hole.   If the number of drill sizes can be kept to a minimum, the cost of the PCB will be reduced since it will take less time to switch between sizes when the PCB is being made.
The drl file shows the exact locations of each hole.  It is sorted by the tool number tool number so the PCB manufacturer knows the size and location of all the holes for a specific drill bit size.
In addition, there are two Gerber files that are related to PCB drilling.  The Drill and Drill Symbols are created when the Gerber RS-274Xis selected and subsequently these files are used in documentation such as the assembly drawing to verify all hole sizes and drill locations are correct.
The Drill Gerber file shows round images at each hole with the radius of the image the same as the hole radius.  When viewing this layer, the user can observe the hole sizes, locations and relations to other locations on the PCB.
The Drill Symbols Gerber file has symbols shown for each tool.  For example, if there are 5 different hole sizes needed for drilling into the PCB, there will be 5 different symbols on this Gerber layer.



3. Next Step

Now that you have finalized your design it is time to review the files for fabrications. 
This final article in this series is a prototyping check-list for any engineer looking to use a quick-turn PCB fabrication house, such as PCBWay (www.pcbway.com/e)



website: www.pcbway.com/e




For PCB prototype, please feel easy contact Erin KOU (erin.kou@pcbway.com)

2015年6月10日星期三

PCB share: 20 Tips for Engineering Students

20 Tips for Engineering Students


Getting your engineering degree is a ticket to rewarding careers, and sometimes a handsome paycheck. But before you enter the field as a professional engineer, some serious studying, a few late nights, and a few tips to get you through your first year are in order.

Tip #1: Take good notes, and keep them all after your classes are over.

Engineering textbooks can be dense, but endure through the tedium. Do your reading – all of it – and keep a highlighter and page markers handy. After the class is over, keep your most useful and well-written textbooks as reference. Your notes, annotations, and highlighting will be invaluable later on. You may even want to keep a “Rules of Thumb” notebook, allowing you quick access to your most-used formulas.

Tip #2: Get to know your professors.

Develop a relationship with your professors so you feel comfortable approaching them and asking for help. Get to know one or two key professors particularly well, and turn to them for help with your homework, insight into the industry, and even job or program references.

Tip #3: Ask questions, both in class and out.

Your professors want you to learn. But if the only thing you ever ask is, “Will this be on the test?” then you are not taking advantage of their knowledge or willingness to help. Ask for additional examples to clarify difficult equations and concepts. More often than not, your fellow students will thank you for speaking up, and your professor will appreciate your active investment in the material.

Tip #4: Try to solve a problem before asking for help.

No one wants to do your homework for you. You’ll be more likely to get help if you’ve already begun the effort. Even if you’re totally lost, make a legitimate, prolonged effort to solve a problem before asking for help. When you do seek help, be prepared to discuss what you tried already, and bring your scratch paper showing your attempts.

Tip #5: Form a study group.

Working alone can get exasperating if you find yourself stuck on a problem. Working with others will not only introduce other viewpoints to approaching a problem, it will also provide encouragement and camaraderie in the face of frustration.

Tip #6: Teach someone else.

One of the most effective ways of ensuring you understand something is by explaining it to someone else. Before you move past a subject, make sure you not only answered the question but also can replicate and explain the process. Each new subject and concept will build on the last, so don’t move on until you’ve mastered each new idea.

Tip #7: Diversify your engineering classes.

Take classes in all sorts of engineering, even if they are not your concentration. Understanding not only the subject matter, but also how other types of engineers approach and solve problems, will lend insight into your own field, from biomedical to mechanical to chemical to environmental engineering and beyond.

Tip #8: Take classes outside engineering, particularly design classes.

The most successful engineers are insatiable learners, so seek to broaden your skill set generally. A design class can teach you how to represent information visually and how to talk about an idea from a big picture perspective. A writing class can hone your skills for communicating your ideas to others. A business class can prepare you for organizational tasks and leadership roles later in your career.

Tip #9: Hone your communications skills, including conversation, writing, and presentation.

The best and most innovative ideas in the world have no hope of growing past the drawing board if you are unable to communicate them effectively. And today, most technical communication between team members and leadership happens over email, which is a form of writing. Learn to present an argument simply and without agenda, and always read your emails through once or twice before sending.

Tip #10: Learn another language.

Engineering knows no political or cultural borders; engineers are in demand everywhere in the world. Increase your worth by becoming proficient in another language, and don’t be afraid to think of your career on a global level. Want to build bridges in China? You should learn Mandarin.

Tip #11: Build your portfolio.

Participate in as many hands-on projects as possible, especially those outside the classroom. Future employers look for both coursework and relevant experience, and a well-organized and articulate portfolio will be invaluable during your job search. Your practical project experience will also reinforce the “in theory” knowledge you gain in class.

Tip #12: Get a summer internship.

One of the best portfolio buildings blocks is the summer internship. Internships do more than build your resume; they demonstrate to potential employers that you can commit to a long-term role and work as part of a team.

Tip #13: Build your network.

Do not wait until you need a job to start building professional relationships. In addition to getting to know your professors and peers, attend extracurricular lectures, workshops, and networking events, and get to know as many people working or studying in your field as possible. Take a genuine interest in the work of others, ask lots of questions, and don’t be afraid to seek guidance or advice from those of advanced experience. They were once neophyte engineers too!

Tip #14: Scour the resources of professional engineering associations and companies.

Professional engineering associations, such as the National Society of Professional Engineers, are an invaluable resource for jobs, advice, and networking. Identify organizations that share your values and interests, and make as many contacts as possible.

Tip #15: Skip the honors class.

In the engineering field, your GPA matters. If you struggle in calculus, don’t kill yourself in Honors Calc; take the easier class, learn the material thoroughly, and take the higher grade.

Tip #16: Learn when to lead and when to back down.

Engineers often work in teams, and every team has one or more leaders. You should feel comfortable in both leading and following the directions of others. Hone your leadership skills and learn how to effectively influence group decisions, but recognize when your contribution should be to take orders and follow direction.

Tip #17: Work on the problem before the team meets.

The best results occur when a group discusses ideas that have already been fleshed out by individual members. Learn to do your own work and self-motivate. Always arrive at the team meeting with ideas in mind.

Tip #18: Be a perfectionist.

In the words of one engineer, “In the working engineer world, a 99% correct product can cost millions of dollars in damages.” Adopt the mindset of practicing something until it is perfect, as opposed to going as quickly as possible and settling for a B. When your work is 100%, even if it is slower, it is valuable.

Tip #19: Identify your inspiration.

What made you decide to study engineering? Who do you look up to in your chosen field? Learn about how individuals and companies have sought and found success, and replicate their behaviors.

Tip #20: Take heart and persevere.

Engineering is a difficult course of study for everyone, no matter their IQ or test scores. Frustration can lead to feeling like an imposter. Every future engineer has struggled through seemingly impossible problem sets, cranky professors, and gut-wrenching exams. In the face of inevitable small failures, recognize that you are challenging yourself like never before, and push on through the difficult experiences.




website: www.pcbway.com/e




For PCB prototype, please feel easy contact Erin KOU (erin.kou@pcbway.com)


2015年6月8日星期一

Top 10 PCB Design Software That You Can Use

Top 10 PCB Design Software That You Can Use


By Gulshan jassal  Shared by Erin KOU (PCBWay)

Here is the some of the best PCB design software that can help you to develop your projects. PCB known as the Printed circuit board  that’s are used in the all kinds of the electronics equipments and Gadgets.
The PCB are covered the large technology part for designing the hardware nowdays. There are the various software are used for designing the these boards in order to before they are put in the production.
These software are satisfied different need according to the industry requirement. In this top PCB design software some of the software are industry standards  and beginner level of user (educational use Only) compatible that you can use.

Top 10 PCB Design Software  That You Can Use For Your Different Purpose

  1. bestPCB software
ZinetPCB is the best professional and personal used PCB design software you design free layouts and circuits design.
best free pcb software
This is the Free open source software that run on Windows it is very esay to use and more fast and less complicated
best free pcb software
This program is printer generated output comes under the Mac OS work pretty well on apple Mac OS
best free pcb software
4. TinyCad
This software comes under its own library and very easy to understand layout you can make your free circuits.tinycad-1
This program can used the printer the created the outputs and very user friendly and make your circuits more comparible and good design
best free pcb software
  This software allows the user to produce electronic circuits, while also teaching them more about them
This software allows the user to produce electronic circuits, while also teaching them more about them
This program can be used for the creation of printer circuit boards and electronic schematic diagrams.
8.gEDA
This is a quite popular software that works on Linux. It has been used fr electrical circuit design, prototyping, simulation, schematic capture and production.
This software has been designed to reduce the design to production time. It is one of the most popular electronics design software.
This is a free and open source PCB editor that runs on Windows and was released under the GNU General Public License.

website: www.pcbway.com/e




For PCB prototype, please feel easy contact Erin KOU (erin.kou@pcbway.com)

2015年6月7日星期日

The Engineer’s Guide To High-Quality PCB Design

The Engineer’s Guide To High-Quality PCB Design

Author:  Nicholaus Smith (Application engineer) Sharee by Erin KOU
Eventually, almost every EE must design a PCB, which isn’t something that’s taught in school. Yet engineers, technicians, and even novice PCB designers can create high-quality PCBs for any and every purpose with confidence that the outcome will meet or exceed the objective. Also, these designs can be completed on schedule and within budget while meeting the design requirements. Designers just need to mind the essential documentation, design steps and strategies, and final checks.

Table of Contents

  • The Basic Design Process
  • Bill Of Materials
  • PCB Documentation
  • Schematic Details
  • Component Placement
  • Thermal Issues
  • Fine-Tuning The Component Placement
  • Summary
  • References
The Basic Design Process
The ideal PCB design starts with the discovery that a PCB is needed and continues through the final production boards (Fig. 1). After determining why the PCB is needed, the product’s final concept should be decided. The concept includes the design’s features, the functions the PCB must have and perform, interconnection with other circuits, placement, and the approximate final dimensions.
1. The ideal PCB design flow begins when designers recognize a need that must be fulfilled, and it doesn’t end until testing verifies that the design can meet those needs.

1. The ideal PCB design flow begins when designers recognize a need that must be fulfilled, and it doesn’t end until testing verifies that the design can meet those needs.

Ambient temperature range and concerns regarding the operating environment should be addressed and used to specify the materials selected for the PCB. Components and PCB materials must be selected to guarantee operation under all expected and potential forms of duress the board may be exposed to during its lifetime.
The circuit schematic is drawn based on the concept. This detailed diagram shows the electrical implementation of each function of the PCB. With the schematic drawn, a realistic drawing of the final PCB dimensions should be completed with areas designated for each of the circuit’s schematic blocks (groups of components closely connected for electrical reasons or constraints).
Bill Of Materials
Simultaneously with the schematic’s creation, the bill of materials (BOM) should be generated. The components in the circuit should be selected by analyzing the maximum operating voltages and current levels of each node of the circuit while considering tolerance criteria. With electrically satisfactory components chosen, each component should be reconsidered based on availability, budget, and size.
The BOM must be kept up-to-date with the schematic at all times. The BOM requires the quantity, reference designators, value (numeric value of ohms, farads, etc.), manufacturer part number, and PCB footprint for each component.
These five requirements are critical because they define how many of each part are needed, explain identification and circuit locations while exactly describing each circuit element used for purchasing and substitution, and explain the size of each part for area estimations. Additional descriptions may be added, but it should be a condensed list describing each circuit element, and too much information can over-complicate library development and management.
PCB Documentation
The PCB’s documents should include the hardware dimensional drawings, schematic, BOM, layout file, component placement file, assembly drawings and instructions, and Gerber file set. User guides also are useful but aren’t required. The Gerber file set is PCB jargon for the output files of the layout that are used by PCB manufacturers to create the PCB. A complete set of Gerber files includes output files generated from the board layout file:
  • Silkscreen top and bottom
  • Solder mask top and bottom
  • All metal layers
  • Paste mask top and bottom
  • Component map (X-Y coordinates)
  • Assembly drawing top and bottom
  • Drill file
  • Drill legend
  • FAB outline (dimensions, special features)
  • Netlist file
The special features included in the FAB outline include but are not limited to notches, cutouts, bevels, back-filled vias-in-pad (used for BGA-type IC packages that have an array of pins under the device), blind/buried vias, surface finish and leveling, hole tolerances, layer count, and more.1
Schematic Details
Schematics control the project, so accuracy and completeness are critical for success. They include information that is necessary for the proper operation of the circuit. A schematic should include adequate design details, such as pin numbers, names, component values, and ratings (Fig. 2).
2. Proper schematics, such as this one for the IDTP9021R wireless power receiver’s buck regulator block, include pin numbers, names, component values, ratings, and other vital details.
2. Proper schematics, such as this one for the IDTP9021R wireless power receiver’s buck regulator block, include pin numbers, names, component values, ratings, and other vital details.

Consider assembly when designing footprints, and follow the manufacturer’s recommended PCB footprint. Some components come in microscopic packages and do not allow room for extra copper. Even in these cases, a stripe of 2.5 to 3 mils of solder mask should be applied between every pin on the board.Embedded within each schematic symbol is the manufacturer part number used to determine price and specifications. The package specification determines the size of the footprint for each component. The first step should be to make sure the exposed copper for each pin is in the proper location and is slightly larger than the component pins (3 to 20 mils) depending on available area and soldering method.
Follow the rule of 10. Small vias have a finished hole size of 10 mils with 10 additional mils of pad ring. Traces should be 10 mils or further from the edge of the board. Trace-to-trace pitch is 10 mils (5-mil air-gap, 5-mil trace width, 1-oz copper). Vias with 40-mil diameter holes or larger should have a pad ring added for reliability. An additional 15 to 25 mils of clearance beyond the design rule should be instated for copper planes on outer layers from plane to pins. This reduces the risk of solder bridging at all solder points.
Component Placement
Component placement is next in the process and determined based on thermal management, function, and electrical noise considerations. A first-pass component placement step commences after the outline of component and interconnect position has been assigned. Immediately after the individual components are placed, a placement review should be held and adjustments made to facilitate routing and optimize performance.
Placement and package sizes are often reconsidered and changes are made at this point based on size and cost. Components absorbing greater than 10 mW or conducting more than 10 mA should be considered powerful enough for additional thermal and electrical considerations. Sensitive signals should be shielded from noise sources with planes and be kept impedance-controlled.  
Power management components should utilize ground planes or power planes for heat flow. Make high-current connections according to the acceptable voltage drop for the connection. Layer transitions for high current paths should be made with two to four vias at each layer transition.Place multiple vias at layer transitions to increase reliability, reduce resistive and inductive losses, and improve thermal conductivity.
Thermal Issues
The heat generated by the IC is transferred from the device to the copper layers of the PCB (Fig. 3). The ideal thermal design will result in the entire board being the same temperature. The copper thickness, number of layers, continuity of thermal paths, and board area will have a direct impact on the operating temperature of components.
3. IC thermal conduction can be achieved through the use of thermal vias and copper planes.
3. IC thermal conduction can be achieved through the use of thermal vias and copper planes.

To reduce operating temperatures easily, use more layers of solid ground or power planes connected directly to heat sources with multiple vias. Establishing effective heat and high-current routes will optimize heat transfer by means of convection. The use of thermally conductive planes to spread the heat evenly dramatically lowers the temperature by maximizing the area used for heat transfer to the atmosphere (Fig. 4).2
4. Effective heat spreading can distribute the heat uniformly from a heat source to all of the PCB’s exposed surfaces.
4. Effective heat spreading can distribute the heat uniformly from a heat source to all of the PCB’s exposed surfaces.

With even heat distribution, the following formula can be used to estimate surface temperatures:
P = (heatConvection) x area x (ΔT)     
where:
P = power dissipated on the board
Area = board (X axis x Y axis)
ΔT = surface temperature – ambient temperature
HeatConvection = convection constant based on ambient conditions
Fine-Tuning The Component Placement
Components should be placed in the following order: connectors, power circuits, sensitive and precision circuits, critical circuit components, and then the rest. The schematic is built around each part on the PCB and completely interconnected. Routing priority for the circuit is chosen based on power levels, noise susceptibility, or generation and routing capability.
In general, trace widths of 10 to 20 mils are used for traces carrying 10 to 20 mA and 5 to 8 mils for traces carrying less current than 10 mA. High-frequency (greater than 3 MHz) and rapidly changing signals should be carefully considered when routed along with high-impedance nodes.
The lead engineer/designer should review the layout, and physical locations and routing paths should be adjusted iteratively until the circuit is optimized for all design constraints. The number of layers depends on power levels and complexity. Add layers in pairs since the copper cladding is produced that way. The routing of power signals and planes, the grounding scheme, and the board’s ability to be used as intended all influence operation.
Final inspections should involve verification that sensitive nodes and circuits are properly shielded from noise sources, solder mask exists between pins and vias, and the silkscreen is clear and concise. When determining layer stack-up, use the first inner layer below the component sides as ground and assign power planes to other layers. Stack-ups are created in a manner that balances the board relative to the midpoint of the Z axis.
Consider any concerns the PCB designer has during the reviews, and correct the PCB based on feedback generated by the reviews. Create and verify lists of changes during each review iteration until the board is finalized. During all stages of the layout, keep the design error free by using the design rule checker (DRC).
The DRC can only catch errors that it has been programmed to monitor, and DRC rule sets often change based on individual designs. At the minimum, the design rule checking should cover package-to-package spacing, unconnected nets (a unique name identifying each node of the circuit), shorted nets, air-gap violations, if vias are too close to solder pads, if vias are too close to each other, and vertical clearance violations.
Many other important DRC rules can be set to ensure a robust design, and they should be researched and understood. For example, keep clearances at or above 5 mils. Vias should not be located within surface-mount pads (unless back-filled). And, solder mask should be between all solder points.
Cost is often a driving influence behind PCB design, so it is good to understand the cost adders in PCB manufacturing. A typical board is two to four layers, with no drill holes less than 10 mils in diameter and 5-mil minimum air gaps and trace widths. It also should be 0.062 in. thick with standard FR-4 and a copper foil weight of 1 oz. Additional layers, extra thick or thin boards, vias-in-pad, back-filled vias (non-conductive preferred due to conductivity limitations and thermal expansion differences), blind/buried vias, and lead time all substantially add to the overall cost.
Manufacturer capabilities should be understood when the PCB design commences. PCB fabs are routinely contacted about capabilities and cost reduction techniques when designing PCBs for manufacturability.
Summary
PCB design may be complex, but it is quite possible to design good boards with a little technique and practice. Using these guidelines and adding research when needed, seasoned veterans may continue honing their skills and novice designers may learn to create high-quality PCBs that exceed expectations.
References
1. Cohen, Patricio, Concepts and terminology used in Printed Circuit Boards (PCB), Electrosoft Engineering, Web, May 25, 2013.
2. Mauney, Charles, Thermal Considerations for Surface Mount Layouts, Texas Instruments, Web, May 13, 2013.

website: www.pcbway.com/e








For PCB prototype, please feel easy contact Erin KOU (erin.kou@pcbway.com)